Xov Xwm Kev Lag Luam

Txheej txheem cej luam cable

2021-03-03

Txheej txheem cej luam cmuaj peev xwm

 

1. Basebandcoaxialcmuaj peev xwm

 

Cov coaxialcmuaj peev xwm siv lub zog tooj liab hlau ua cov tseem ceeb thiab txheej txheej ntawm cov khoom siv insulating. Qhov txheej txheej ntawm cov ntaub thaiv insulating yog puag ncig los ntawm cov ntaub ntom ntom ntom, thiab lub vas yog them nrog txheej txheej ntawm cov khoom thaiv. Muaj ob txoj kev siv cov coaxialcmuaj peev xwm. Ib qho yog 50-ohm cmuaj peev xwm, uas yog siv rau kev xa xov digital, thiab tseem hu ua baseband coaxialcmuaj peev xwm vim nws feem ntau siv rau kev xa xov hauv qhov xov; lwm qhov yog 75-ohm cmuaj peev xwm, uas yog siv rau kev xa xov hluav taws xob, uas yog lub xov tooj broadband coaxiallos sib tham txog ntu tom ntej. Qhov sib txawv no tshwm sim los ntawm keeb kwm vim li cas, tsis yog lub laj thawj kev tsim khoom lossis chaw tsim khoom.

 

Cov qauv ntawm cov coaxialcmuaj peev xwm ua rau nws muaj cov bandwidth loj thiab cov yam ntxwv ua suab nrov zoo tshaj plaws. Qhov bandwidth ntawm ib coaxialcmuaj peev xwm nyob ntawm lub cmuaj peev xwm ntev. Ib txoj kab hluav taws xob 1km tuaj yeem ncav cuag cov ntaub ntawv sib kis ntawm 1Gb / s ~ 2Gb / s. Cov xov hluav taws xob ntev kuj tseem siv tau, tab sis qhov kis tau tus mob yuav tsum raug txo kom tsawg lossis nruab nrab amplifiers yuav tsum siv. Tam sim no, coaxialcmuaj peev xwms feem ntau hloov los ntawm cov xov hluav taws xob, tab sis lawv tseem siv dav hauv cmuaj peev xwm TV thiab qee cov koom tes hauv cheeb tsam.

 

2. BroadbandCoaxialCmuaj peev xwm

 

A coaxialcmuaj peev xwm system that uses a limited TV cmuaj peev xwm for analog signal transmission is called a broadband coaxialcmuaj peev xwm. The term "broadband" comes from the telephone industry and refers to a frequency band wider than 4kHz. However, in computer networks, "broadband cmuaj peev xwm" refers to any cmuaj peev xwm network that uses analog signals for transmission.

 

Because the broadband network uses standard cmuaj peev xwm television technology, the usmuaj peev xwm frequency band is up to 300MHz (often to 450MHz); due to the use of analog signals, an electronic device needs to be placed at the interface to convert the bit stream entering the network into an analog signal, and Convert the signal output from the network into a bit stream.

 

Broadband systems are divided into multiple channels, and TV broadcasting usually occupies 6MHz channels. Each channel can be used for analog TV, CD quality sound (1.4Mb/s) or 3Mb/s digital bit stream. TV and data can be mixed on a single cmuaj peev xwm.

 

A major difference between a broadband system and a baseband system is that because the broadband system covers a wide area, it requires an analog amplifier to periodically strengthen the signal. These amplifiers can only transmit signals in one direction. Therefore, if there are amplifiers between computers, packet packets cannot be transmitted backwards between computers. To solve this problem, two types of broadband systems have been developed: dual-cmuaj peev xwm systems and single-cmuaj peev xwm systems.

 

1) Dual cmuaj peev xwm system

 

A dual cmuaj peev xwm system has two identical cmuaj peev xwms laid side by side. In order to transmit data, the computer transmits the data through the cmuaj peev xwm 1 to a device at several roots of the cmuaj peev xwm, that is, the head-end, and then the head-end transmits the signal down the cmuaj peev xwm through the cmuaj peev xwm 2. All computers send via cmuaj peev xwm 1 and receive via cmuaj peev xwm 2.

2) Single cmuaj peev xwm system

 

Another solution is to allocate different frequency bands for internal and external communications on each cmuaj peev xwm. The low frequency band is used for communication from the computer to the top device, and the signal received by the top device is moved to the high frequency band and broadcast to the computer. In the subsplit system, the 5MHz~30MHz frequency band is used for inward communication, and the 40MHz~300MHz frequency band is used for outward communication. In the midsplit system, the inward frequency band is 5MHz~116MHz, and the outward frequency band is 168MHz~300MHz. This choice is caused by historical reasons.

 

3) Muaj ntau txoj hauv kev los siv broadband.

A dedicated permanent channel can be allocated between a pair of computers; other computers can apply to establish a temporary channel through the control channel, and then switch to the applied channel frequency; and all computers can share one or a group of channels. Technically speaking, broadband cmuaj peev xwms are worse than baseband (single channel) cmuaj peev xwms in sending digital data, but its advantage is that it has been widely installed.